Spark plug gap setter



May l5, 1951 M. A. BRETSCH ET AL 2,553,169

SPARK PLUG GAP SETTER Filed May 21, 1949 n 2 Sheets-Sheet l l INVENToRs:

MICHAEL A. Bans/:1f

- RUBEHTKEHHISTIE May l5, 1951 M. A. BRETSCH ET AL 2,553,169

SPARK PLUG GAP SETTERv Filed May 21, 1949 `2 Sheets-Sheet 2 n A i! l IN VEN TORS: Mmm/3 ABRBTMH,

BY amr K. Ummm Patented May 15, 1951 SPARK PLUG GAP SETTER Michael A. Bretsch and Robert K. Christie, To-

ledo, Ohio, assignors to Champion Spark Plug Company, Toledo, Ohio, a corporation of Dela- Ware Application May 21, 1949, Serial No. 94,658

1 Claim.

This invention relates to means for setting the gaps of spark plug electrodes, and particularly ground electrodes of the multiple prong type commonly used in aviation spark plugs.

An object of the invention is the provision of a simple and enicient means that is easily operable to simultaneously apply a yielding predetermined inward pressure to opposing electrodes to set them in predetermined spaced relation to the common center electrode without danger of cracking the nose portion of the spark plug insulator.

Further objects and advantages of the invention will be apparent from the following description, and from the accompanying drawings illustrating one embodiment of the invention, in which- Fig. 1 is a side elevation of an apparatus embodying the invention, with a spark plug in gap setting position therein and with the pressure parts in releasedV position; Fig. 2 is a top plan view thereof; Fig. 3 is a section on the line 3-3 of Fig. 2; Fig. 4 is an enlarged plan View of the apparatus, with parts broken away and with the gap setting members in electrode engaging positions; Fig. 5 is a section on the line 5-5 in Fig. 4, and Fig. 6 is a section on the line 6--6 in Fig. 4.

Referring to the drawings, I designates a standard for mounting on a work bench, or the like, and secured to the top of this standard by screws 2, or the like, is a top member 3. This member has a short arm 4 projecting upward from the standard and a long arm 5 projecting laterally therefrom. The arm 5 has a vertical opening 6 therethrough that is oblong lengthwise of the arm and in which a spark plug receiving bushing 'i is floatingly mounted. In the present instance, the bushing has it upper end radially flanged to set on the upper marginal edge wall of the opening 5 and is of a diameter to substantially t the width of the opening 6, so that the bushing may have limited floating movements lengthwise of the arm 5. A split spring ring 8 is seated in an annular recess in the bushing below the arm and coacts with the lower edge wall of the opening to retain the bushing therein.

A spark plug 9 to be adjusted is placed in the bushing I with its ring end up and with its shell shoulder i0 seating on an internal flange II in the lower end of the bushing. The maximum diameter of the shell is somewhat less than the internal diameter of the bushing to permit an easy sliding of one with the other. The spark plug has the customary center electrode I2 and side or ground electrodes I3. The side electrodes are of the multiple prong type and, in the present instance, project inwardly from a ring I4 thatY is xedly attached to the exposed end of the shell I5 of the plug, as well understood in the art. The side electrodes have their free end portions angled outwardly lengthwise of the plug and terminating in spaced relation to the center electroole. The side electrodes erode in use and thus require adjustment inwardly towards the center electrode to re-establish the proper gap setting.

The outer end of the arm 5 is provided with an upwardly extending fork I6 in which is pivoted a thrust nnger I'I for vertical swinging movements and adapted to extend inward from its pivot on a slight downward angle from the horizontal so that its nose may engage in the angle of an adjacent side electrode I3 of a spark plug mounted in the bushing 1. A spring nger I8 bears against the inner end of the thrust finger Il, and when the finger is in elevated position the spring acts to hold it in such position, as shown in Fig. 1.

The inner end portion of the member 3 is vertically slotted at 20 (Fig. 6), and mounted within such slot on a pivot ZI is a vertically swinging rocker arm 22. This arm extends upward from its pivot a distance above the arm 5 and has a thrust finger 23 projecting inwardly at substantially a right angle thereto from a slot in its outer v end. The finger is normally held in the outwardly retracted position shown in Fig. 1 by a coiled expansion spring 24 (Fig. 6). When swung inwardly from such position, the free end of the nger 23 engages the angle of that electrode I3 opposing the one engaged by thrust finger II.

The means for applying inward movement to the arm 22 comprises a cam 25 that is iixedly mounted on a rock-shaft 29 in the fork of the arm 4 and acts against a roller on the arm 22. The shaft 26 is journaled in the arm 4 and extends a distance from a side of the arm. A block 2l is rotatably mounted on the outer end of this shaft and has a lost motion connection. therewith through a pin 28 projecting from the shaft into a segmental slot 29 in the block. A handle or lever arm 30 extends radially from the block. The block and shaft are yieldngly connected by a. coiled spring SI, which has engagement at one end with a pin 32 on the block and at its other end with a pin 33 on the shaft. The spring 3| normally holds the block 21 in position for the left hand wall of the slot 29 to engage the pin 28. As indicated in Figs. 1 and 3, a swinging of the handle 30 in counterclockwise direction will cause the block to turn on the shaft away from the pin 28 and to apply a yielding turning force to the shaft and its cam 25 through the spring 3 I The initial movement of the power applying block, and until the torque finger 23 engages the respective electrode I3, is practically unopposed so there is no relative movement of the block 28 on the shaft. The continued movement of the block 21, necessary to cause the opposing fingers II and 23 to cooperate to eiect the desired gap setting of the opposing electrodes I3, now transmits yielding force to the shaft through the spring 3I due to the lost motion pin-and-slot connection between the block and shaft. Thus, the operator, by watching the movement of the pin 28 within its slot 29, can determine the gap setting pressure applied to the finger 23 and discontinue the movement at the desired point. An index mark on block 21 can be correlated with the position of pin 28 to show when the proper pressure has been applied to the electrode. -It is thus possible to obtain a uniform setting of the gaps in successive plugs without danger of applying so much pressure to the electrodes that fracture of the spark plug core might take place.

The width of the spark gap or space between the side and center electrodes is determined by a gauge member 35 that has two laterally spaced gap lingers 3S at its inner end adapted to straddle the center electrode I2 of a spark plug and provide a i'lrm spacing means of predetermined thickness between it and two opposed side electrodes. The operator holds the gauge 35 in position with one hand while using the other hand to operate the handle 36 to apply the desired gap setting torque to the shaft 26 and to the two opposed electrodes I3 engaged by the gauge member.

When the gap has been properly set for two opposed side electrodes I3., the handle 35 is moved in clockwise direction to the position shown in Fig. l, so that the thrust finger 23 and its carrying arm 22 are retracted to inoperative position by the action of the spring 2. The finger I'I is also raised to the upright position shown in Fig. l and the gauge member 35 is removed from engagement with the spark plug. This having been done, the spark plug is turned in the bushing to bring the next pair of side electrodes I3 into line with the gap setting ngers I1 and 23, and the gauge is replaced with its fingers in gap spacing relation between such electrodes and the center electrode. The ringer I'I is then turned down into engagement with its adjacent electrode and the handle 3E! op erated to position the linger 23 in engagement with the electrode nearest it and to apply the necessary gap setting pressure thereto. This setting pressure is determined by the extent of movement of the pin 28 in the slot 29. and when the pin has assumed a predetermined position in such slot the operator knows that the necessary pressure has been applied. During the positioning of the ngers I'I and 23 in engagement with the electrodes and the application of a gap setting pressure thereto, Vthe spark plug is permitted to freely move transversely with the bushing 1 in the arm opening 6 lengthwise of the arm, thus eliminating all strain from the spark plug tending to crack its insulator.

We wish it understood that our invention is not limited to any specific construction, arrangement or form of the parts, as it is capable of ,numerous modifications and changes without departing lfrom the spirit of" the claim.

Having thus described our invention, what we claim as new, and `desired to secure by United States Letters Patent, is:

sure to the swinging pressure iinger to apply a gap setting pressure to .the engagedV electrode in opposition to said thrust linger.

MICHAEL A. BRETSCI-I.

40 ROBERT K. CHRISTIE.

REFERENCES CITED The following references are of' record in the file of .this patent:

UNITED STATES Pii'nrrrrsV Number Name Date 608,012 Y SICkleI July 25, 1898 2,321,854 Rabezzana et al. June 15, 1943 `2,383,953 Coombs Nov. 5, 1945 FQREIG'N PATENTS Number Country I Date 622,641 France Marj?, 1928 In an apparatus of the class described, aV 

